I have a 99 F-150 5.4 w/ 3.73 rear gears and a towing package. The truck has 118,000 miles, all highway. Up until 3 wks ago it ran perfectly. I had the transmission rebuilt and the Ford factory trailer wiring harnesses installed instead of the monkey fist wiring job that the trailer dealer did. The truck has developed a nasty ping if I run it on 87 octane, and it pings a little on hard acceleration with premium.Today coming back from Gainesville it pinged a lot with premium. It also seems to have developed what seems to be an exhaust leak, because it makes a ticking noise at higher RPM's. I took the truck to my garage and they checked the codes. Nothing turned up. They then pulled out a TSB that described my problem and said it was a bad mass air flow sensor. They disconnected the sensor and I drove it for a few minutes and the pinging went away. They then reconnected the sensor. I have to order a new sensor, which I dont mind doing, but I dont want to just stand back and throw money at the truck trying to fix it. Does their solution sound reasonable, and does anybody have any opinions on what it might be?

 

Since the sensor was disconnected and it ran ok, that would work for me. Also no codes show up. So, what else are you going to look for? Sounds like you may have a very good garage to go to.

 

Sounds like the faulty MAS is making your engine run lean, thus the pinging. If you need to replace the MAS you might also consider going to an aftermarket item like Pro-M. You can gain an additional 8-12 hp by going to a MAS with more flow. Just a thought.:-)

 

I had this same problem on my 94 t-bird with the 4.6. cleaned the mass air sensor and the pinnging stopped.to do this remove the sensor from the vehicle.the sensor has two very small wires that get coated with crud.take a Q tip and saturate it with windex then very gently scrub the two wires being careful to not bend or break them. hope this helps.